Z.ai’s flagship reasoning model, released August 2026 with open weights. It reuses GLM 5.2’s base model, so every gain comes from post-training, and it always thinks before it calls a tool.
Paste a server URL, pick a model, and watch it call your tools in a real conversation. No install.
No server of your own? Leave it blank and use one of the public mock servers.
MCP Evals
Can GLM 5.3 actually complete tasks with your server?
One chat shows the tool calls work. An eval writes real tasks from your tool schemas, has GLM 5.3 drive each one, and reports where it got the wrong answer even though every call succeeded. Pick GLM 5.3 as the driver.
GLM 5.3 is a 744B-parameter mixture-of-experts model with 40B active per token. Z.ai built it for complex software engineering and long-horizon agent work, and post-trained it heavily on security tasks. It takes text only; GLM 5.3 Flash is the multimodal tier. Z.ai launched it on its API and GLM Coding Plan on 14 August 2026 and published the weights on Hugging Face on 28 August under its own GLM-5.3 licence.
These are the vendor’s own claims, not measurements of ours. Run the model against your own server to find out whether they hold for your tools.
Run GLM 5.2 and GLM 5.3 on the same four-step task against the complex-schema mock: create_user_profile, process_order, analyze_data, then configure_workflow. Same base model, different post-training, so any difference in the calls comes from the post-training alone. All the mock servers →
| Model | Model ID |
|---|---|
| GLM 5.3 | z-ai/glm-5.3 |